The present invention generally relates to a system and method for controlling the position of a radiographic device. More particularly, the present invention relates to a system and method for automatically positioning an image receptor based on the position of a manually positioned diagnostic source assembly in an X-ray imaging device.
Radiographic imaging systems are used for a wide variety of applications in the medical field. One example of a radiographic imaging system used in medicine is an X-ray imaging system. X-ray imaging systems are typically used for diagnostic purposes in the medical field. Typical X-ray imaging systems operate by transmitting X-radiation or X-rays through a patient""s body using a diagnostic source assembly (xe2x80x9cDSAxe2x80x9d). The DSA is typically a device that is capable of transmitting X-rays through the body of a patient. The position of the DSA is typically adjustable and the DSA is generally placed over the area of a patient""s body that is being imaged. Once properly positioned, the X-rays transmitted through the patient""s body by the DSA are more absorbed by dense structures in the body such as bones, and less absorbed by less dense structures such as tissue and organs. The X-rays passed through the patient""s body are then typically received by an image receptor located beneath the patient. Typically, the image receptor is comprised of either an X-ray film or a digital solid state detector.
In order to achieve an X-ray image with sufficient information and contrast to provide a doctor with the diagnostic information needed, precise alignment of the DSA and the receptor often needs to be achieved. Typically, the DSA projects a beam of X-rays toward the image receptor surface and through body structure of the patient being imaged. The area of projected X-rays that is incident on the image receptor defines the active imaging area (AIA). Generally, the X-ray beam field or field of view (FOV), which is the intersection of the projected beam and the image receptor plane, must be coincident with, or lie within, the boundaries of the image receptor surface in order to avoid loss of image data. The FOV may be adjusted by rotating or tilting the DSA to vary the direction of the projected X-ray beam, and also by operating a collimator to vary the width and length dimensions of the X-ray beam. Further adjustments may also be made by linear translation of the DSA or the image receptor.
When the DSA is oriented so that the X-ray beam is directed in perpendicular or orthogonal relationship to the image receptor plane, the image receptor may be located directly below the DSA. However, X-ray technicians or operators may need to angulate the DSA with respect to the image receptor, that is, rotate or pivot the DSA so that the beam is not projected perpendicular to the image receptor. Angulation of the DSA may be desirable, for example, to ensure that the beam passes through a specific body structure of the patient, or to avoid imaging specific structures. As the DSA becomes increasingly angulated, the image receptor typically needs to be positioned at a location offset from the position of the DSA in order to receive the X-rays. Typically, the greater the degree of angulation the DSA is from perpendicular to the image receptor, the greater the offset between the image receptor and the DSA need to be. Therefore, in order to ensure the image receptor receives the X-rays from the DSA, the operator typically needs to precisely position the image receptor so that it is in the X-ray beam""s FOV.
In the absence of optimal or appropriate alignment of the DSA and the image receptor, anatomical cutoff may occur during the imaging process. That is, the bodily structures intended to be imaged may not be completely imaged due to the incorrect offset between the DSA and the image receptor. Anatomical cutoff may necessitate that the imaging be repeated, which may increase procedure cycle time, raise examination costs, and expose the patient to higher levels of net radiation.
In typical prior art systems, efforts to attain the precise alignment of the DSA with the image receptor desired for successful imaging has been attempted by one of two methods. The first method typically used to align the DSA and image receptor is through direct alignment. That is, physically attaching the DSA to the image receptor in the desired alignment. The second method typically used to align the DSA and image receptor is through indirect alignment methods. That is, positioning the DSA and the image receptor individually when they are not attached together. Both methods are further described below.
In typical X-ray imaging systems that utilize direct alignment of the DSA and the image receptor, the DSA and the image receptor are physically attached to each other by a rigid structure. The DSA is typically attached in a perpendicular alignment to the image receptor so that the X-ray beam transmitted by the DSA will be transmitted directly into the flat plane of the receptor. In direct alignment systems, the DSA and the image receptor are typically not moveable or able to be repositioned by an operator or X-ray technician. Because of the rigidly fixed positioning of the DSA and the image receptor, X-ray imaging systems that utilize direct alignment may suffer from a number of drawbacks.
One drawback that may occur in direct aligned X-ray imaging systems is lack of flexibility in positioning of the system by the operator. That is, when the position of the system is fixed, the operator may have to adjust the patient""s position in order to get an image. During imaging procedures it may be more difficult to adjust the patient to the X-ray system than it is to adjust the X-ray system to the patient. However, in a direct aligned system only limited adjustment of the system is possible. Therefore, if patients are required to hold difficult or uncomfortable positions in order to fit into the X-ray imaging system, bad images may be generated and frequent retakes may be required. Requiring frequent retakes may often be time consuming and may expose the patient to excess radiation. Additionally, with direct aligned X-ray imaging systems, retakes may be further complicated by patient access. That is, once a determination has been reached to retake an image, the patient may have exited the system or may have to be re-scheduled. Also, direct aligned X-ray imaging systems are less desirable because the systems are typically quite complex and costly.
In order to overcome some of the drawbacks related to the rigid inflexibility of direct aligned systems, some prior art X-ray systems have utilized indirect alignment methods. That is, the DSA and the image receptor are not physically attached to each other and may be individually positioned by an operator. Individually positioning the DSA and the image receptor may help give the operator more flexibility and may allow for better patient comfort than direct aligned systems. Typically positioning of the DSA and receptor in indirect aligned systems has been achieved by one of two methods. The first method typically used in indirect alignment systems involves manual positioning of both the DSA and the image receptor by an operator. The second method typically used in indirect alignment systems is motorized positioning of both the DSA and the image receptor.
In typical indirect alignment systems manually positioned, an operator physically positions the DSA and the image receptor by hand. Generally, at first, the DSA may be manually positioned by the operator in a position appropriate for the area of the patient""s body being imaged. Next, the patient is typically positioned so that the area of the patient""s body to be imaged is comfortably positioned with respect to the DSA. Finally, the image receptor may be manually positioned by the operator in the proper alignment with the DSA. The operator may use a visual light field projected by the DSA on to the patient or receptor to judge where the DSA should be positioned with respect to the patient and the image receptor. Once the operator concludes that the DSA and the image receptor have been optimally aligned, the image may be taken. While the manual positioning of the DSA and the imaging receptor by the operator may allow much greater flexibility to the operator than in direct alignment systems, a number of drawbacks with manual positioning may result.
One drawback that may occur in manually positioned indirect alignment systems is inconsistent alignment. Because the DSA and the image receptor are both manually positioned by the operator, the operator must judge when the DSA and image receptor are in optimal alignment. While the visual light field discussed above may help aid the operator in their judgment, it still may be difficult for the operator to precisely determine when the DSA and image receptor is in optimal alignment. Inconsistent alignment of the DSA and the receptor by the operator may result in poor quality images, anatomical cutoff, or may require frequent retakes. As mentioned above, frequent retakes may increase imaging time and expose the patient to excess radiation.
An additional drawback which may occur in manually positioned indirect alignment systems is the increased time required to position the DSA and the image receptor. Because the operator must judge and manually position both the DSA and the image receptor, proper alignment may require some time. The operator may have to position and then reposition the DSA, the image receptor, or both numerous times before an optimal alignment may be achieved. Therefore, the xe2x80x9ctrial and errorxe2x80x9d nature of manually positioning both the DSA and the image receptor may increase the time required to take good images. Increased time may result in reduced throughput of the imaging department of the medical facility, which may be busy during a typical day.
The second method typically used in indirect alignment systems is motorized positioning of both the DSA and the image receptor. That is, the operator uses controls to position a motorized DSA and a motorized image receptor into proper alignment with each other. In typical motorized positioning systems, the operator may use the controls to position the motorized image receptor into a position appropriate for the area of the patient""s body being imaged. Next, the patient is typically positioned so that the area of the patient""s body to be imaged is comfortably positioned over the image receptor. Finally, the motorized DSA may be positioned by the operator using the controls in the proper alignment with the image receptor over the area of the patient""s body to be imaged. Once the operator concludes that the DSA and the receptor have been optimally positioned, the image may be taken. While the motorized positioning of the DSA and the image receptor by the operator may allow greater precision to the operator than in manually positioned indirect alignment systems, a number of drawbacks with motorized positioning may result.
One drawback that may be present in motorized positioning systems is loss of freedom of motion of the DSA and the image receptor. That is, the range of motions available to the motorized DSA and the motorized image receptor may be less than the range of motion available to the manually positioned system. Having reduced range of motion may limit the ability of the operator to quickly and efficiently align the DSA and the image receptor. The operator may have to adjust the patient to compensate for the reduced range of motion that may be available to the motorized positioning system. Having to adjust the patient and not being able to position the DSA and the receptor in exactly the desired position may result in poor images and the need for retakes. As described above, poor imaging and retakes may have adverse effects on the patient and hospital throughput.
Another disadvantage that may be present in motorized positioning systems is the amount of time required to position the system. Typically, positioning the DSA and the image receptor by motorized control is slower than manually positioning the DSA and the receptor, particularly when the displacements are large. Thus, if multiple images from different angles or retakes are required, the increase in imaging time due to the motorized positioning of the DSA and the image receptor may be significant. As mentioned above, increasing the imaging time may lead to reduced throughput and back-ups in the imaging department of busy hospitals. Additionally, motorized positioning systems fail to address the various preferences or needs of an operator to move the positioning system at a slower or faster rate, as desired. That is, motorized positioning systems may not provide continuously variable of proportional speed control as desired by an operator.
Thus, a need exists for a positioning control system for a medical imaging device, such as an X-ray imaging device, that combines the optimal alignment properties of a direct alignment system with the flexibility of an indirect alignment system. A need further exists for a positioning control system that allows for quick and precise alignment of a diagnostic source assembly and an image receptor.
The preferred embodiment of the present invention provides a system and method for automatically positioning an image receptor based on the position of a manually positioned diagnostic source assembly (DSA) in an X-ray imaging system. In operation, a patient whom the X-ray imaging will be performed on is placed on the examination table of the imaging system. An X-ray technician or operator then manually positions the DSA over the area of the patient""s body to be imaged. Once the DSA is manually positioned in the proper location by the X-ray technician, position sensors in the DSA transmit the lateral, longitudinal, vertical, and angular orientation of the DSA to a system controller. The system controller calculates the optimal position of the image receptor based on the position of the DSA. The system controller then transmits the optimal position to a motor drive that automatically positions the image receptor in the optimal position. Once the image receptor has been positioned in the optimal position by the motor drive, sensors in the image receptor transmit the positional data of the image receptor to the system controller. The system controller then verifies that the image receptor has been positioned in the correct location. If the system controller determines that the image receptor has been properly positioned, the X-ray imaging may then occur. If the system controller determines that the image receptor has not been properly positioned, the X-ray technician may override the motor drive and manually position the image receptor in the desired location.